JP4262782B2 - LAMINATE MANUFACTURING METHOD AND LAMINATE OBTAINED BY THE METHOD - Google Patents

Abstract

The invention pertains to a method for making a laminate comprising at least the following steps: placing a metal sheet on a form tool or a substrate, placing an adhesive layer on top of the first metal sheet, placing a second metal sheet on top of the adhesive layer such that at least one of the metal sheets overlaps at least one edge of the other metal sheet, applying heat and pressure to the thus obtained stack, where during the application of pressure at least one of the metal sheets is bent towards the plane of the other metal sheet. Thus, complicated structures can be optimized for a certain application and, besides, manufactured in one go using comparatively inexpensive tools.

Description

The present invention comprises at least the following steps:
Placing a first metal sheet on a form tool or substrate;
Placing an adhesive layer on the first metal sheet;
Placing the second metal sheet on the adhesive layer such that at least one metal sheet overlaps at least one edge of the other metal sheet;
Heat and pressure are applied to the laminate so obtained (ie, mainly or exclusively on the side of the laminate not facing the mold or substrate);
The present invention relates to a method for producing a laminate or laminate.
Such a method is known, for example, from US Pat. No. 5,429,326 which discloses laminated fuselage panels in aircraft applications. The panel comprises at least two metal layers with an adhesive layer between them. The metal layer is substantially coplanar and consists of two or more sheets or sections separated by so-called splices or splice lines. The patent describes a method in which the splice in the first metal layer is parallel to the splice in the second adjacent metal layer and spaced from it on the sides. By using this staggered cross-lamination, the maximum width of the laminate is no longer limited to the width of the metal sheet or portion, which is limited to about 165 cm in current manufacturing techniques.
Another advantage is that the spliced laminate of U.S. Pat. No. 5,429,326 surprisingly has an increased residual strength (i.e., a load parallel to the splice) when compared to a non-spliced laminate. For example, strength after the laminate is damaged by impact).
However, to prevent exposure of the splice to environmental conditions and to increase the tensile strength of the laminate at and near the splice in the metal layer (with respect to lateral loading on the splice line), the so-called doubler splice It is desirable to cover some) (in many cases, as defined by safety regulations).
FIG. 1 shows three aluminum layers (12) and two fiber-reinforced adhesive layers between aluminum layers (12) (13; each of these layers is two unidirectional prepregs, ie 90 ° relative to the other. FIG. 2 is a schematic cross-sectional view of a spliced metal polymer laminate (11 in FIG. 1) consisting of a prepreg containing rotated vertical and parallel filaments. Each aluminum layer (12) consists of two or more aluminum sheets (14) separated by a splice (15). A doubler (16), which is a metal polymer laminate, cross-links to the splice (15) in the upper aluminum layer (12) of the spliced laminate (11) and is attached thereto by a curable adhesive (17).
The manufacture of the structure of FIG. 1 includes several process steps (spliced laminate (11) and doubler (16) manufacture, then bonding the two) and, for example, a spliced laminate ( If the doubler (16) has to be bonded to both sides of 11), it requires a very expensive or bonded mold that is machined to fit the doubler in contact with the mold. Furthermore, when the laminate is used in aircraft skins, the doubler (16) forms protrusions that impair the appearance and aerodynamic properties.
The object of the present invention further extends the splicing concept disclosed in US Pat. No. 5,429,326, in particular by solving the problems caused by the use of doublers and other irregularities in the laminate. And improve it. This and the following objectives are achieved by applying the method described in the first paragraph of this specification. During the application of pressure, at least one of the metal sheets bends (i.e., exits from its own plane) toward the plane of the other metal sheet, and the form of the metal sheet is fixed.
This method involves the application of heat and pressure and prior to fixing or freezing the strain in the laminate, for example by curing, evaporation of the solvent contained in the adhesive, or cooling the adhesive to a temperature below Tg, It effectively utilizes the low bending stiffness of uncured laminates, i.e., metal and adhesive layer laminates. The present invention allows each metal layer to take the form of a laminate just below it.
Preferably, the metal sheet is displaced at a distance that is at least about the same as the thickness of the adhesive layer or the thickness of the adhesive layer and the metal sheet.
FIG. 2 shows the structure obtained by the method of the invention using a single autoclave cycle (time: about 1 hour) at normal pressure and heat levels, ie 5 bar and 120 ° C. A mold (2024-T3 having a thickness of 21 mm, having a thickness of 21 mm and subjected to an alkaline degreasing treatment, then etching or anodizing, and applying a primer) having a flat smooth surface ( (Not shown). Three aluminum layers (22; 2024-T3 having a thickness of 0.3 mm and treated in the same way as the doubler (21)), and two adhesive layers (23; each layer between the aluminum layers (22) Three layers of unidirectional S2-glass fibers (0 ° -9 ° -0 °) in F185 exHexcel are layered over the doubler (21) and the aluminum layer (22) closest to the doubler (21) A splice (24) is placed in the middle along the width of the doubler (21). A second doubler (25) is placed on the aluminum layer splice farthest from the first doubler (21). Adhesive (26; AF163-2K ex 3M) is present between the doubler (21, 25) and the aluminum layer (22). Next, heat and pressure are applied (to the surface shown as “the inner surface of the fuselage structure”). During this time, the spliced laminate is bent around the doubler (21), and the adhesive layer (23) and the adhesive (26) are cured. At the position of the doubler (21), the layer of the spliced laminate is curved to form a sufficiently (aerodynamic) flat surface with the doubler (21).
Of course, the present invention is not limited to a doubler or the like. FIG. 3 shows the so-called ply-drop-off obtained by the method of the invention. The lower metal layer (31) and the adhesive layer (32) serve as a substrate, which becomes an integral part of the laminate, and on the substrate, the first metal layer (33), the adhesive layer (34), In this case, the second metal layer (35) which is the upper layer is laminated later. Upon application of pressure, the second metal layer slowly takes the form of the end of the prepreg. It is preferred to use an additional adhesive (36) near the end of the adhesive layer (34). When the adhesive layer (34) has two or more prepregs, it is preferable to increase the number of prepregs stepwise from the end of the second metal sheet (35). Therefore, the change in thickness becomes more gradual.
The ply-drop-off obtained by the method of the present invention is stronger, less susceptible to delamination, and the change in thickness is much more gradual than the prior art.
As is apparent from the foregoing description, the present invention provides great freedom to the laminate designer. 4 and 5 show other examples of advantageous embodiments of the invention.
FIG. 4 shows an alternative to the use of the separation doubler described above. By using the splice (41) formed as an overlap, a part of the metal layer (42) functions effectively as a doubler.
One airline or other airplane owner wants what is called a so-called “bright-skin aircraft”. For this purpose, the outer surface of the aluminum sheet used for the skin is provided with a cladding (generally a thin metal layer of aluminum). For polymer-metal laminates, this means that the outer aluminum sheet (42, 44) has a cladding layer on one side (denoted "outer surface of fuselage structure") and the cladding layer is over Means also present in the splice formed as a wrap (41). In the aircraft industry, it is preferable not to bond metals in the cladding zone because these bonds are critical to the integrity of the aircraft's main structure and the interaction between the cladding and adhesive in a corrosive environment is undesirable. This is because it may cause In addition, adhesive fillets (26 and 43 in FIGS. 2 and 4, respectively), typically having a width of 6-10 mm, remain visible to the naked eye on the outer surface of the unpainted fuselage skin.
For the above reasons, the shapes shown in FIGS. 2 and 4 are less desirable in the “gloss skin aircraft”. However, both problems (cladding in the coupling zone and wide visible fillet) are solved by another more preferred embodiment of the invention shown in FIG. Instead of placing the doubler (51) directly on the mold, it is overlaid on the substrate (mounted on the mold), in which case the metal layer (53) is separated by the splice (52). Consisting of at least two metal sheets or parts. The metal sheet constituting the metal layer (53) is clad only on the surface in contact with the mold and becomes an integral part of the laminate. During the application of pressure and heat, the doubler (51) and the metal layer (53) are not deformed, while other parts of the spliced laminate (metal layer and prepreg) are around the doubler (51). Bend.
The virtual bonding zone is embedded in the laminate and has no cladding. Furthermore, a very thin (0.1-0.6 mm) splice (52) is only visible on the outer surface of the skin of the fuselage structure.
Another advantage of this shape is the small edge of the outer surface of the aluminum metal sheet when a polished fuselage skin is required (the part of the metal sheet that contacts the adhesive must be anodized and primed) The elimination of the need for only anodization and priming (ie, the overlap in FIG. 4) and, in the painting aircraft, avoiding damage to the bonding zone during (periodic) paint removal.
The mold and substrate on which the metal layer and the adhesive layer are laminated need not be a flat plate. For example, for an aircraft, it can be shaped as a negative of a single or double curved fuselage panel or other desired shape. In this way, rather than first making a flat laminate by lamination and curing and then shaping the laminate, a panel or other desired shape is produced in one go. The radius of the single curved fuselage panel used for the fuselage is preferably in the range of 1-7 m. By the way, using a mold shaped to meet the requirements of the final product (at least some of the requirements), reducing the process steps, i.e. not having many local distortions that are the object of the present invention. That is very useful in itself.
The laminate of the present invention preferably has from 2 to about 20 metal layers and from about 1 to about 19 adhesive layers. The metal layer is preferably less than about 1.5 mm, more preferably about 0.1 to 0.9 mm, and most preferably about 0.2 to 0.5 mm. In a preferred embodiment, the metal layer is about 0.3 mm (0.012 inches) thick.
The metal sheet is preferably manufactured from a metal having a tensile strength of 0.20 GPa or more. Examples of suitable metals are aluminum alloys, steel alloys, titanium alloys, copper alloys, magnesium alloys, and aluminum matrix composites. AA2000 series aluminum-copper alloys, AA3000 series aluminum-manganese alloys, AA5000 series aluminum-magnesium alloys, AA7000 series aluminum-zinc alloys, and AA6000 series aluminum-magnesium-silicon alloys are preferred. Some particularly preferred alloys are AA2024 aluminum-copper, AA7075 aluminum-zinc, and AA6013 aluminum-magnesium-silicon. Two preferred alloys are AA2X24-T3 and AA7X75-T6. If superior corrosion resistance is desired, a sheet of AA5052 alloy is included in the laminate. Furthermore, the laminate disclosed in US Pat. No. 5,547,735 comprising at least two metal sheets, each of which is a sheet of a different alloy, is also very suitable for use in the present invention.
It is understood that bending in a metal sheet includes both elastic and plastic strain components. Which component dominates depends primarily on the type of material, dimensions, and manufacturing conditions.
The adhesive layer is preferably reinforced with (glass) fibers. If a splice is present in the laminate, it is preferred that a portion of the (glass) fiber is cross-linked to the splice and is generally continuous in close proximity to the splice line. Depending on the loading conditions of the structure, the fibers are oriented individually or in groups, in one direction or in several different directions. It is preferred that at least about half of the fibers extend perpendicular to the adjacent metal layer splice. In a particularly preferred embodiment, about half of the fibers are oriented in the 0 ° direction (longitudinal direction), while the other half is oriented in the 90 ° direction (lateral direction). Alternatively, about one third of the fibers are oriented at 0 ° and about two thirds are oriented at 90 °, or about two thirds are oriented at 0 ° and about one third. Are oriented at 90 °.
The adhesive layer preferably comprises a synthetic polymer. Examples of suitable non-thermoplastic polymers are epoxy resins, unsaturated polyesters, vinyl esters, phenolic resins, and thermoplastic resins. Suitable thermoplastic polymers are, for example, polyarylate (PAR), polysulfone (PSO), polyethersulfone (PES), polyetherimide (PEI), or polyphenylene ether (PEE), polyphenylene sulfide (PPS), polyamide-4 , 6, polyketone sulfide (PKS), polyetherketone (PEK), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). As noted above, in addition to the adhesive that is part of the adhesive layer, an adhesive (eg, the adhesive indicated by the numbers 17, 26, 36, 43, 54) is locally applied to other parts of the laminate. Used. In principle, all adhesives suitable for use in the adhesive layer are also suitable for use as “local” adhesives.
The adhesive layer has the same thickness as the metal layer. The adhesive layer is preferably less than about 1.5 mm, more preferably about 0.1 to 0.9 mm, and most preferably about 0.2 to 0.5 mm thick. An adhesive layer with a thickness of about 0.3 mm (0.012 inches) is used in the preferred embodiment.
Preferred fibers for reinforcing the adhesive layer are continuous fibers or filaments of materials such as glass, aromatic polyamide (aramid), and carbon. Preferred glass fibers are S-2 glass fibers or R-glass fibers, containing about 58-69 wt% SiO ₂ , 18-29 wt% Al ₂ O ₃ , and 7-19 wt% mGo, respectively. Low cost of E- glass fibers containing from about 55 wt% SiO _2, 15 wt% Al ₂ O _3, 19 wt% CaO, 7 wt% B ₂ O _3, and 3 wt% MgO, are also suitable. One suitable aramid fiber is made from poly-para-phenylene terephthalamide. The fiber has a modulus of about 60-650 GPa and an elongation at break of about 0.2-8%. The fibers are preferably continuous filaments each having a diameter of about 3 to 30 microns.
Preferred laminates are reinforced with S-2 glass fibers in the adhesive layer. The S-2 glass fibers preferably have a diameter of about 8-12 microns, which constitutes about 35-75%, preferably about 57-63% of the total volume of adhesive and fiber of the reinforced adhesive layer. To do.
In addition to the materials and shapes described above, reference may be made in particular to EP 056288, EP 056289, EP 312150, and EP 312151, all of which are non-added containing metals suitable for use in the present invention. The present invention relates to a joint metal polymer laminate.
The invention further comprises a laminate (obtained by said method) comprising at least a first metal sheet and a second metal sheet, and at least one adhesive layer applied between and bonded to the metal sheet. And at least one of the metal sheets (top view) overlaps at least one edge of the other metal sheet, and the at least one metal sheet bends toward the plane of the other metal sheet, preferably further in the plane Relates to a substantially elongated laminate. Preferably, additional adhesive is applied to the area where the metal sheets overlap.
These laminates can have a flat surface, despite the presence of "irregular" such as doublers, and can be manufactured in a single manufacturing cycle using relatively inexpensive molds. It is therefore relatively inexpensive, allows for the production of spliced panels with reduced weight and can have a high strength ply-drop-off shape. In addition, tests on these laminates have shown that they have substantially similar mechanical properties (ie, excellent fatigue resistance, high residual strength, fire resistance, corrosion resistance, etc.) as conventional metal-polymer laminates. Indicated.
Another advantage is that the interference of splice components (eg splice lines, doublers) with respect to aircraft-designed structural components (eg stringer positions, shear clades, window frames, doors) can be kept to a minimum. Yes, the reason is that the minimum thickness step in the new concept is smaller than in the conventional manufacturing method (compare FIGS. 1 and 3) and is actually the maximum thickness step that is further cross-linked by the stringer from 0.5 to This is because it is smaller than 0.6 mm.
The invention further relates to a vehicle, a spacecraft or aircraft structural member comprising the laminate of the invention, and an aircraft comprising the laminate.
EP 502620 is superplastically moldable in areas where additional strength is required, or in areas where excessive elongation occurs during molding, otherwise the area is locally thinned or weakened. An additional sheet or doubler of material is disclosed to be superimposed on the main sheet of material (before superplastic forming) (see, for example, the summary of the patent application and FIG. 7). Metal-polymer laminates are not disclosed, and in practice the disclosed superplastic forming process is not well suited for the production of such laminates.
Within the scope of the present invention, the term “top view” shall be understood as being parallel to the normal of the surface of the metal sheet. The “plane of the metal sheet” is a plane in the portion of the metal sheet that is not displaced or deformed. Of course, this plane may be curved.

Claims (14)

Placing at least a first metal sheet on a mold or substrate;
Placing an adhesive layer on the first metal sheet;
Placing the second metal sheet on the adhesive layer such that at least one metal sheet overlaps at least one edge of the other metal sheet;
A method for producing a laminate comprising the steps of applying heat and pressure to the laminate thus obtained,
A process for producing a laminate, characterized in that at least one metal sheet is bent towards the plane of another metal sheet during the application of pressure, after which the form of the metal sheet is fixed. The method according to claim 1, wherein the second metal sheet is bent toward the plane of the first metal sheet. The method according to claim 1 or 2, characterized in that the surface of the mold or substrate facing the laminate is substantially smooth and / or curved. The method according to claim 1, wherein the adhesive layer comprises at least one prepreg. The first metal layer is a doubler, and the second metal layer has a splice disposed at or near the center of the first metal layer. The method described. The method according to claim 1, wherein the substrate comprises at least one metal layer and at least one adhesive layer. The adhesive layer between the first metal sheet and the second metal sheet comprises at least two prepregs, and the number of prepregs increases stepwise from the ends of the overlapped edges The method as described in any one of Claims 1-4. The method according to claim 1, wherein the substrate is a metal layer. At least a first metal sheet and a second metal sheet, and at least one adhesive layer applied between and bonded to the metal sheet, wherein at least one metal sheet is at least one of the other metal sheets Laminate overlapping at one edge, characterized in that at least one metal sheet bends and / or substantially extends into the plane of the other metal sheet. 10. Laminate according to claim 9, characterized in that it has a doubler. The laminate according to claim 9 or 10, wherein the adhesive layer contains reinforcing fibers. The adhesive layer between the first metal sheet and the second metal sheet comprises at least two prepregs, and the number of prepregs increases stepwise from the ends of the overlapped edges. The laminate according to any one of Items 9 to 11. A vehicle, spacecraft or aircraft structural member comprising the laminate according to any one of claims 9-12. An aircraft comprising the laminate according to any one of claims 9-12.

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